The simulated CH₄ flux

<p><strong>Figure 4.</strong> The simulated CH₄ flux. (a) The monthly CH₄ fluxes from 1961 to 2080. (b) The change of the CH₄ flux between the recent and the future periods. Values are for the wetland fraction of the study area only.</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

The simulated NEE flux (kg C m⁻² yr⁻¹) (uptake: negative; release: positive)

<p><strong>Figure 3.</strong> The simulated NEE flux (kg C m⁻² yr⁻¹) (uptake: negative; release: positive). (a) The inter-annual variations of the NEE flux (above) and the 2 m air temperature (below) in the CRU-forced run and the RCAO-forced run. (b) The change of the NEE flux between the recent and the future periods in the RCAO-forced run. Note: 1 kg C m⁻² corresponds to 17.9 Gt C in this domain.</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

The change of the simulated albedo between the recent and the future periods

<p><strong>Figure 5.</strong> The change of the simulated albedo between the recent and the future periods. (a) Summer albedo change. (b) Winter albedo change.</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

Dominant vegetation distribution

<p><strong>Figure 1.</strong> Dominant vegetation distribution. (a) A composite vegetation map based on a potential natural vegetation (PNV) map (Kaplan <em>et al</em> <a href="http://iopscience.iop.org/1748-9326/8/3/034023/article#erl475802bib24" target="_blank">2003</a>), the IGBP land cover dataset 2000–2001 (Friedl <em>et al</em> <a href="http://iopscience.iop.org/1748-9326/8/3/034023/article#erl475802bib14" target="_blank">2010</a>), and the Circumpolar Arctic Vegetation Map (Walker <em>et al</em> <a href="http://iopscience.iop.org/1748-9326/8/3/034023/article#erl475802bib47" target="_blank">2005</a>). (b) The recent dominant PNV simulated by the CRU-forced run. (c) The recent dominant PNV simulated by the RCAO-forced run. (d) The future dominant PNV simulated by the RCAO-forced run. *: the color of IBS represents temperate needle-leaved evergreen forest in the sub-plot (a).</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

Tree-line

<p><strong>Figure 2.</strong> Tree-line. (a) The simulated tree-line comparisons between the CRU-forced run and the RCAO-forced run. (b) The recent and the future tree-line comparisons in the RCAO-forced run. (Green: the CAVM tree-line boundary; blue: tree-line advance for the latter; red: tree-line retreat for the latter; gray: no difference.)</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

The change of simulated latent heat flux associated with modeled species composition in terms of LAI fraction

<p><strong>Figure 6.</strong> The change of simulated latent heat flux associated with modeled species composition in terms of LAI fraction. (a) The change of latent heat flux between the recent and the future periods. (b) Species transition at location (66.46° N, 153.76° E), denoted as the red triangle in (a). (c) Species transition at location (60.87° N, 21.83° E), denoted as the red star in (a).</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

The NEE and CH₄ flux simulated by the CRU-forced run and the RCAO-forced run (uptake: negative, release: positive)

<p><b>Table 1.</b>  The NEE and CH₄ flux simulated by the CRU-forced run and the RCAO-forced run (uptake: negative, release: positive). CH₄ values are for the wetland fraction of the study area only. </p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p